The development of media communications technologies leads to increasingly vigorous demands on application of multiple media streams; application of merely one video stream plus one audio stream cannot meet people's pursuit of multiple screens and multiple scenes. A typical example is that multiple displays are provided at a telepresence conference site, and images of multiple participants and a presentation material can be simultaneously displayed on different displays, so as to provide a more vivid immersive experience.
However, in a transmission process of a media stream, the media stream is generally transmitted from a network environment to another network environment, and therefore problems such as network address translation (NAT)/firewall (FW) traversal may be involved. An idea of solving the problems is to perform mapping on ports, that is, one-to-one mapping is performed between the ports. However, when the number of media streams increases, the number of ports that need to be mapped also increases, which results in complexity of the NAT/FW traversal operations and a large system overhead, and therefore occurrence of multiple streams has a relatively great impact on an entire network. An existing solution is, between a sending end and a receiving end, multiple media streams are sent and received at a same port, that is, a port is multiplexed to transmit the multiple media streams. However, in a transmission process, how to perform media stream transmission bandwidth adjustment on multiple media streams transmitted at a same transmission port when congestion occurs or congestion is resolved becomes a problem to be solved.
According to a solution in the prior art such as a communications apparatus disclosed by a patent application whose application number is CN201080020341.5 and publication date is Apr. 18, 2012, in a case in which a congestion level exceeds an evaluation value, the communications apparatus cuts off transmission of at least a stream that is in multiple streams transmitted concurrently and has a priority lower than those of the other streams, where a priority of each stream is described by priority information in a storage unit. The communications apparatus evaluates the congestion level in communication using a congestion window in the Stream Control Transmission Protocol (SCTP). However, at present, the SCTP is not widely used. The SCTP is for connection-based transmission. In practice, the User Datagram Protocol (UDP) is used for real-time audio and video streams, where the UDP is for connectionless-based transmission. Parallel transmission in the SCTP does not involve port multiplexing. UDP port multiplexing involves only one Internet Protocol (IP) address and only one port, but the parallel transmission of the SCTP needs multiple IP addresses and multiple ports. In addition, priority information of the SCTP is stored at a local end, and when congestion occurs, a problem that “a stream that a viewer at a receiving end is interested in is cut off because a sender considers the stream to be unimportant” may occur.
In conclusion, how to perform media stream transmission bandwidth adjustment on multiple media streams transmitted at a same transmission port when congestion occurs or congestion is resolved has become an urgent problem to be solved in the industry.